After pleading guilty to reduced charges in the death of her ex-husband, earlier this summer, a Grass Valley woman has been sentenced to three years in prison. 38-year-old Desiree Hayden was originally charged with murdering 44-year-old Brian Sharp, in June of last year. But Nevada County District Attorney Cliff Newell says an autopsy showed that Sharp could have died from a variety of causes, including an assault, a heart condition, drugs found in his body, or a combination…